1. Field of the Invention
The present invention relates generally to a transmitter constituting a basic transmission path (network), and more particularly to a transmitter which has an optical line interface as a service interface, and enables a change of a path line connection by a cross connection switch.
2. Description of the Related Arts
In recent years, a ratio of IP (internet protocol) data abruptly increases in an increasing digital data transmission.
An IP data network is characterized in having an aspect that a service provider other than an operational company holding a basic transmission path (network) operates the network.
FIG. 1 is a configuration diagram of a basic network 1 and an IP data network 2. In the basic network 1, a plurality of transmitters NE (network equipment): A to C are connected between a transmission path (ac), a transmission path (ab), and a transmission path (bc).
The plurality of transmitters NE (network equipment): A to C have each optical line transmission and reception parts a1, a2, b1, b2, c1, c2 for accomodating a service interface in a portion of connecting with the transmission path. Furthermore, the transmitters NE (network equipment): A and C have optical line transmission and reception parts a3, c3 for accomodating the service interface in a portion of connecting with the IP data network 2.
Each optical line transmission and reception part further has a MUX (multiplex)/DMUX (demultiplex), and it is possible to multiplex in a time division the plurality of service interfaces to be accomodated.
The basic network 1 is interfaced with the IP data internet via an optical line (OC3/OC12/OC48, etc.). In the example of FIG. 1, the interface is made via interface lines 3, 4 of the OC12 (600M: ST12 band width).
Furthermore, the transmitters NE: A to C have cross-connection parts (a4, b4, c4 in FIG. 1) which can optionally connect with a path transmission path, and control parts (a5, b5, c5 in FIG. 1) for controlling correspondingly the cross-connection parts a4, b4, c4.
IP units D, E in FIG. 1 are a router, an edge switch, or the like constituting the IP data network 2, and are maintained and operated by the service provider holding the IP data network 2.
Each transmitter NE has a switch SW (c6 in FIG. 1) for relieving a corresponding path line when a fault (an optical line fault, a human fault due to an error connection of the cross-connection) within the basic network occurs, and it is possible to construct a redundancy of the path line.
A meshing region of the transmission paths (ab, bc, ac) in FIG. 1 indicates a band allocated in the basic network 1 as a communication path between the IP unit D and IP unit E (reference symbols Pac, Pab, Pbc in FIG. 1).
Furthermore, transmitters NE: A, and NE: C receive also optical lines af, cg with a conventional voice switch (F/G in FIG. 1).
According to a change of a type of service interface received by the IP units D, E, or a reception data amount, it is possible to use 12×STS1 in the OC 12 interfaces 3, 4 in FIG. 1 in free comparison with STS1/STS3C (3×STS1)/STS12C (12×STS1). However, it is impossible to exceed 12×STS1.
As shown in FIG. 1, in order to take a redundancy, the path line which is transmitted from the IP unit D is transmitted to both a direction of a transmission path (ab) and a direction of a transmission path (ac). The path line received from both the transmission paths is selected by a switch SW part c6 in the transmission unit NE: C, and reception data are sent to the interface line 4 with the IP unit E.
In FIG. 1, in the transmitter NE: B, in order to relay the path line between the IP units D and E, the band allocated to the path is controlled by a control part b5 for the cross-connection b4, thereby securing the band.
At this time, the allocation (a ratio of STS1/STS3C/STS12C) within the band (12×STS1) allocated between the IP units D and E has to be established equally with respect to all the transmitters NE: A to C within the basic network 1.
This establishment is indicated in any type of path formats of STS1/STS3C/STS12C by a CI (concatenation)-ID. This CI-ID is relayed by all the transmitters NE of the basic network 1 between the IP units D and E.
Furthermore, the CI-ID has to agree an expectation of all the path line transmission part of the transmitter NE with the reception part thereof. Accordingly, in the case where, in the prior art, the expectation CI-ID at a reception side does not agree with a reception CI-ID, it is judged that an error connection is made in the cross-connection part, etc. in the transmission path, and a relief is made by the SW part c6, etc. to take a redundant protection.
On the other hand, since conventional voice data transmission data are based on a long-termed transmission path plan such as an installation plan of a SW (switcher), a band change was rare. On the contrary, according to an increase in a recent abrupt IP network and a change to a new type of the IP unit, there are many cases where such an optional change occurs that the allocation of a STS band within the optical line of the OC 12, etc. as the service interface is changed frequently.
However, in the conventional unit shown in FIG. 1, each time such a change is necessary, the CI-ID of the respective transmitters NE: A to C within the basic network has been changed. For this reason, maintenance costs of the basic network 1 increase, and such a problem occurs.